I am looking to learn about how one can use group theory methods to obtain the spectrum of a hydrogenic atom algebraically. I have found many such resources online, such as this paper: http://web.mit.edu/lululiu/Public/8.06/paper.pdf
However, most assume more working knowledge of group theory/Lie algebra than I have. Could anyone provide me with a reference to a textbook or paper/article which derives this result without assuming too much background knowledge? I'm looking for something pedagogic.